An aggregated network is made up of multiple networks (called component networks in this document) that are interconnected with one another. An example of an aggregated network is a multimodal transportation network, such as a public transportation system in a metropolitan area, which may include multiple bus and train networks managed by various agencies, with each network offering multiple transit routes. These multimodal transportation networks, more often than not, provide users the choice to transfer across modes or routes, thus creating interconnections between the networks.
Though transportation networks are commonly used as illustrative examples of multimodal or aggregated networks, aggregated networks are also extensively used to capture the structure of a wide variety of complex networks such as biological and utility networks. Aggregated networks could include multiple networks that belong to the same mode (such as multiple bus networks or multiple water supply networks) or multiple networks of dissimilar nature such as bus and train networks or a water network in conjunction with a sewage network and road network.